2023/06/30 by Di Novo, Nicolo' G., Bagolini, Alvise, Pugno, Nicola M.
#FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
paper · doi:10.48550/arxiv.2306.17635
Coalescence-jumping of condensation droplets is widely studied for anti-icing, condensation heat transfer, water harvesting and self-cleaning. Another phenomenon that is arousing interest for potential enhancements is the individual droplet self-ejection. However, whether it is possible from divergent structures without detachment from pinning sites remains unexplored. Here we investigate the self-ejection of individual droplets from divergent, uniformly hydrophobic structures. We designed, fabricated and tested arrays of nanostructured truncated microcones arranged in a square pattern. The dynamics of the single condensation droplet is revealed with high speed microscopy: it self-ejects after cycles of growth and self-propulsion between four cones. Adopting the conical pore for simplicity, we modelled the slow iso-pressure growth phases and the surface energy release-driven rapid transients enabled once a dynamic configuration is reached. In addition to easier fabrication, microcones with uniform wettability have the potential to allow self-ejection of almost all the droplets with a precise size while maintaining mechanical resistance and thus promising great improvements in a plethora of applications.